The present invention relates to a magnetic recording medium mounted on an external storage device of a computer and such a magnetic storage device, a method of manufacturing the magnetic recording medium, and the magnetic storage device using the magnetic recording medium. Specifically, the present invention relates to a magnetic recording medium including a polymer resin substrate, the method of manufacturing such a magnetic recording medium, and the magnetic storage device using the magnetic recording medium described above.
Recently, magnetic recording media mounted on various magnetic storage apparatuses, such an external storage device of a computer, are expected to exhibit a higher recording density. In order to fully utilizing the realized higher recording density, it has been required for the magnetic head, which writes in and reads out data to and from the magnetic recording media, to facilitate lower-height floating characteristics. To realize a magnetic recording media exhibiting a high recording density and compatible with a low-floating-height magnetic head, various compositions and structures have been proposed for the magnetic layer of the magnetic recording media, various materials for the nonmagnetic undercoating layer and various materials for the nonmagnetic substrate. Although aluminum and glass are the main materials for the nonmagnetic substrate at present, a polymer resin substrate, a so-called plastic substrate, has been proposed recently for the nonmagnetic substrate.
In order to facilitate lower-height floating of the magnetic head so that the higher recording density realized in the magnetic recording media may be fully utilized, it is required for the magnetic recording media to be used reliably for a long time in severer environments. It is also required for the magnetic recording media for digital household appliances now under development to be used reliably for a long time in severer environments. The conditions, under which the magnetic recording media are used, extend from very cold −40° C. to very hot and humid 80° C. and 80% (in relative humidity). Some household appliance makers require that the magnetic recording media be working normally for five years under the conditions described above. Moreover, it is indispensable for the magnetic recording media for household appliances to be manufactured with low costs. The polymer resin substrate is very hopeful to meet the demands described above.
Although the polymer resin substrate is hopeful for the substrate of the magnetic recording media, film inflation (a kind of film cleavage) is caused in the magnetic recording media including the polymer resin substrate. For preventing the film inflation from causing, it has been proposed to irradiate plasma or an ultraviolet ray to the polymer resin substrate (cf. Japanese Unexamined Laid Open Patent Application S57-191830). Japanese Unexamined Laid Open Patent Application H03-207012 discloses a plasma activation method for the polymer resin substrates, which facilitates improving the durability of the polymer resin substrates without impairing the properties of the magnetic layer by selecting a material, which does not affect the properties of the magnetic layer, for the material of the electrode, from which plasma is discharged. A method proposed for preventing film inflation from causing deposits a carbon film, the B/A ratio thereof measured by the Raman spectroscopic analysis is high, on a substrate.
However, it has been revealed that the methods described above sometimes fail to prevent film inflation from causing depending on the layer structure and the film deposition conditions for providing magnetic recording media with a higher recording density.
In view of the foregoing, it would be desirable to provide a magnetic recording medium, which obviates the problems described above. It would further be desirable to provide a very durable magnetic recording medium, which exhibits a high recording density, includes a polymer resin substrate, and facilitates preventing film inflation from causing.